Though organic EL display devices with a superior picture quality than liquid crystals and lower power consumption are expected to be the dream panels, the technology for extending the life and increasing the screen size was difficult which has been causing a delay in commercialization. Organic EL display devices, and their light emission principles are well known, and the technology for making their energy consumption extremely low to protect the earth environment is progressing. However, organic EL elements are sensitive to moisture, and organic EL elements are easily prone to degradation and deterioration by moisture. As a result, a decline in quantum efficiency is accelerated, and the life is said to be about 10,000-20,000 hours. That is, the degradation and deterioration of organic EL elements by moisture have made mass production of organic EL display devices difficult.
FIG. 10 shows a prior art of sealing an organic EL display device. In this, a substrate plate 12 is made of glass, resin, film etc. Then, an organic EL element 16 is sandwiched along with a corresponding sealing case 13, the sealing case 13 being made, for example, of a metal. The organic EL element 16 is an element, which has low voltage of about a few volts to tens of volts and is capable of self-light emission. Since the organic EL element 16 is self-emitting type, it has a wide viewing angle and a high visibility. The organic EL 16 element being a completely thin film type solid-state element, can be made small and thin. Adhesive 17 is used for joining the substrate plate 12 and the sealing case 13. Substrate plate 12 and sealing case 13 are secured by joining the substrate plate 12 and the sealing case 13 with adhesive 17. In this manner, intrusion of moisture to the organic EL element 16 through the gap between the substrate plate 12 and the sealing case 13 was prevented in the prior art.
However, in such a technology, there used to be permeation of air or moisture from the adhesive 17, the substrate plate 12 and the sealing case 13, and due to degradation of the organic EL element 16, there were many instances of failure to emit light. To prevent this, a drying agent was provided between the substrate plate 12 and the sealing case 13. However, as the absorption efficiency depends on the material used, it was not possible to realize a performance beyond the absorption efficacy. For example, with a drying agent, only a maximum of about 20000 hours could be guaranteed. With this, if moisture absorption of the drying agent is not possible, the organic EL element 16 deteriorates, and as the number of light emitting elements of the organic EL display device 11 becomes less, the life of the panel itself is shortened. In particular, since the reliability of a panel is affected by natural environmental conditions such as temperature condition, humidity condition and atmospheric condition under which the organic EL display device 11 is used, it was difficult to guarantee a high reliability of the organic EL display device 11.